The Digital Control Soft-Switching Technology Research In Arc Welding Power Inverter

First of all, the paper briefly introduces the developmental status,trend and application of arc welding inverter technique. In order to solve the shortcoming of arc welding inverter at the present time, such as the big switching stress of main power transistor,the large wastage of power source and the low reliability of the system, the settlement of soft-switching technique is brought forward. Following, the paper summarizes several types of soft-switching inverter and compares their performances. According to the result, the PS—FB—ZVZCS—PWM inverter is selected, and then, the working theory and micro changing process of this inverter is particularly analyzed.Secondly, in the design of control circuit, the issue aims to achieve all-digital control. It takes digital signal processor (DSP) TMS320F2812 as a control center to control the whole welding process, output PWM drive signal, communicate with MCU, gathers real-time welding current and voltage sampling, and takes digital PI modulation and adjusts the duty cycle in order to achieve constant current output. In the design of DSP software, the issue highlights the DSP control procedures and digital PI modulation procedures.At the same time, the issue takes complex programmable logic device (CPLD) as an assistant control. It takes digital phase-shifting to PWM signal, makes logic management to welding signals and protecting signals, and then takes them back to DSP. In the design of CPLD software, the issue minutely introduces the digital phase-shifting control procedures and idiographic design process of CPLD.Finally, based on the theory above, we manufacture a sample type of power inverter. Then, we take a temperature-rising test and get some working wave form of the power inverter from oscillograph. The coming results show that, this sample power inverter can achieve zero voltage switch of leading arm in all output range and basically achieve zero current switch of back arm. In addition, this sample power inverter can also greatly reduce the switching wastage and switch stress, keep the output current stable, it is sure to become a new type of welding power with good prospect.